Overview – Three Stages of Memory

There are three memory stages: sensory, short-term, and long-term. Information processing begins in sensory memory, moves to short-term memory, and eventually moves into long-term memory.

Information that you come across on a daily basis may move through the three stages of memory. However, not all information makes its way through all three stages. Most of it is forgotten somewhere along the way. The determination of what information makes its way through the different stages depends on what you pay attention to and process. Information that you pay attention to and process will move to the next stage of memory. However, any information you to do not pay attention to never makes it way to the next stage.

Stages of Memory

Sensory memory – Processes information gathered through your five senses. It holds information for an extremely brief period of time (less than a second) after the original stimulus has stopped.

Short-term memory – holds information you are actively thinking about. It lasts for a very brief time (less than a minute) and can only hold 7 +/- 2 pieces of information at once.

Long-term memory – holds information for long periods even permanently. It seemingly can hold an unlimited amount of information.

Sensory Memory

Sensory memory is the first stage of memory. Its purpose is to give your brain time to process the incoming information.

Sensory memory is not consciously controlled. You subconsciously and continuously gather information from the environment through your five senses. Sensory memory holds impressions of that sensory information that was received by your five senses after the original stimulus has stopped. However, it only holds it for a very brief period, generally for no longer than a second. In order for that information to be retained for longer, it has to continue onto short-term memory.

Most of the information that gets into sensory memory is forgotten. It never makes its way into the second stage of memory because it was never attended to. To get information into short-term memory, you need to attend to it – meaning consciously paying attention to it.

Sensory memory can be observed if you look at an object then close your eyes. As your eyes close, you can notice how the visual image is maintained for a fraction of a second before fading. It is your sensory memory that is holding that image.

Sensory memory also explains why the old 16mm movies shot with 16 separate frames per second appears as continuous movement rather than a series of single still pictures. A visual trace is retained in sensory memory for about a split second. But it holds it long enough to keep the image in your mind until the next still image replaces it.

Basically, sensory memory allows you to see the world as an unbroken chain of events, rather than as individual pieces. This is an example of iconic memory, which is your visual sensory memory.

There are two other types of sensory memory; echoic memory (the auditory sensory) and haptic memory (the tactile sensory).

Types of Sensory memory

Iconic memory is the visual sensory memory that holds the mental representation of your visual stimuli.

Echoic memory is the auditory sensory memory that hold information that you hear.

Haptic memory is the tactile sensory memory that holds information from your sense of feeling.

Short-term Memory

Short-term Memory Short-term memory (STM) is also known as working or active memory. It holds the information you are currently thinking about. This information will quickly be forgotten unless you make a conscious effort to retain it.

Like sensory memory, short-term memory holds information temporarily, pending further processing. However, unlike sensory memory which holds the complete image received by your senses, short-term memory only stores your interpretation of the image.

Temporary Storage

As indicated above, information in short-term memory is not stored permanently. Information passes from sensory memory into short-term memory, where again it is held for only a short period of time. Most of the information stored in short-term memory will only be kept for approximately 20 to 45 seconds. While many of your short-term memories are quickly forgotten, paying attention to the information and processing (encoding) it allows it to continue into long-term memory. Just as sensory memory is a necessary step for short-term memory, short-term memory is a necessary step toward the next stage of retention, long-term memory.

Processing or encoding includes making judgments and assessments about meaning, relevance, and significance of that information. It also includes the mental activities needed to move selected portions of the information into long-term memory. If encoding never happens, the information never gets into long-term memory.

The reason a person forgets the name of someone to whom he or she has just been introduced to is because the name often was never encoded and transferred from short-term to long-term memory.

Limited capacity

Short-term memory not only has a limited time, it also has a limited capacity. It is believed to only hold a few items. Research shows the number is around 7 +/- 2 items. For example, if a person is asked to listen to a series of 20 names, he or she normally retains only about seven names. Typically, it is either the first few or last few. The reason is because if you focuses on the first few items, your STM becomes saturated, and you cannot concentrate on and recall the last series of items. People are able to retain more information using memory techniques such as chunking or rehearsal.

Long-term Memory

Long-Term Memory Long-term memory (LTM) refers to the storage of information over an extended period. It is all the memories you hold for periods longer than a few seconds. The information can last in your long-term memory for hours, days, months, or even years. Although you may forget some information after you learn it, other things will stay with you forever.

Some information retained in STM is processed or encoded into long-term memory. This information is filed away in your mind and must be retrieved before it can be used. Some of the information in your LTM is easy to recall, while other memories are much more difficult to retrieve.

Unlike short-term memory, long-term memory has seemingly unlimited capacity. You may remember numerous facts and figures, as well as episodes in your life from years ago.

Types of long-term memory

There are main two types of long term memory; explicit memory and implicit memory.

Explicit memory

Explicit memory are those experiences that can be intentionally and consciously remembered. It is knowledge or experiences that can be consciously remembered such as facts, data, episodes, or events. Explicit memory can be further sub-categorized as either episodic or semantic memories.

Episodic memory refers to the firsthand experiences that you have had (e.g. episodes or events in your life). For example, you may remember your 16th birthday party or your first soccer game.

Semantic memory refers to knowledge of facts and concepts about the world. For example, you may remember the names of presidents or how to multiple two numbers.

Implicit memory

Implicit memory refers to knowledge that we cannot consciously access. It is remembering without awareness. For example, you may remember how to ride a bike or walk, but it is difficult to explain how you do it.